1. Field
The present disclosure relates generally to apparatus and method for tile and assignment processing, and more specifically to accounting for tiles that have been processed with tile based processing in order to synchronize tile based processing with assignment based processing for improved performance.
2. Background
In communication systems, modulation symbols are processed in regions of frequency and time. In some communication systems such as orthogonal frequency division multiplexed (OFDM) systems, as an example, these regions may be divided into what are termed “tiles,” which are contiguous regions of frequency and time. For example, a tile might comprise 16 subcarrier frequencies over eight time sequential OFDM symbols.
In OFDM systems such as Ultra Mobile Broadband (UMB) as an example, resource assignments allocated to mobile stations for uplink are normally divided among various tiles. Resource assignment processing of received OFDM signals is performed in units of codewords in preparation of error correcting decoding. However, because OFDM symbols are scanned in frequency, rather than time order (i.e., symbols), modulation or tile processing of all of the various tiles that may carry information for a single codeword (or, in UMB, a sub-packet) need to be processed through channel estimation and signal maximizing or noise filtering through techniques such as maximum ratio combining (MRC) or minimum mean square error (MMSE) prior to assignment processing. Additionally, in some systems any given tile may contain portions of multiple sub-packets and may contain more than one layer from respective mobile units, where multiple layers are identical regions of frequency and time that are separable at the receiver using MIMO (multi-input multi-output) transmission techniques. Thus, a tile for one assignment processing of one layer may also be needed for another assignment processing of another layer, which could result in the duplication of tile processing. Therefore, the determination of which tiles need to be tile processed in order to process a particular sub-packet on a particular layer becomes complicated. Accordingly, a need exists to synchronize or coordinate tile and assignment processing in order to optimize processing and avoid duplicate processing of tiles.